Partially qualifying property is subject to the permanent rule if it is installed as part of the interior lighting systems of a building and it is certified that the interior lighting systems that have been incorporated into the building, or that the taxpayer plans to incorporate into the building subsequent to the installation of such property, will reduce the total annual energy and power costs with respect to combined usage of the building’s heating, cooling, ventilation, hot water, and interior lighting systems by 162/3 percent or more as compared to a Reference Building that meets the minimum requirements of Standard 90.1-2001. The required 16-2/3-percent reduction must be accomplished solely through energy and power cost reductions for the heating, cooling, ventilation, hot water, and interior lighting systems. Reductions in any other energy uses, such as receptacles, process loads, refrigeration, cooking, and elevators, are not taken into account in determining whether the 16-2/3-percent reduction is achieved. (reference http://www.irs.gov )